The use of trench cutting machines for laying flexible casings or tubes, e.g. for optical fibers, as well as cables or wires for electrical or other installations is becoming increasingly common. One reason for this is that a narrow trench make less damage on e.g. a road and therefore provides less environmental impact than a wider excavated channel. Furthermore, a narrow cut trench is much easier to cover and can be made almost invisible as if no trenching had been performed. Also, using a circular blade arrangement in a cutting operation makes the side walls of the trench less likely to collapse, since larger stones or roots are cut through. Finally, the material from the trench when using a blade arrangement becomes fine debris which more easily handled that excavated material.
When performing a cutting operation, the circular blade can be rotated in two alternative directions. A first direction involves rotating the circular blade in the same direction as the ground contacting wheels of the machine, which operation is commonly referred to as “down-cut”. A problem with this operation is that cut debris is drawn backwards into the trench by the blade and will partially re-fill the trench unless steps are taken to remove the debris immediately after the circular blade. A second direction involves rotating the circular blade in the opposite direction as the ground contacting wheels of the machine, which operation is commonly referred to as “up-cut”. In this case, the problem of debris gathering in the cut trench is reduced, but debris can be thrown out in front of the machine as the cutting teeth of the blade cuts through the surface. The latter is a particular problem when the circular blade begins its cut into the surface. Also, the cutting action of the blade can induce forces to the machine, which forces can make the machine unstable unless the weight on a rearmost axle of the machine is sufficient to counteract such forces.
Hence, there is a need for a trench cutting machine that solves the above problems. One object of the invention is to provide an improved trench cutting machine that can be operated in a stable manner during the entire cutting operation. A further object is to provide means for controlling the spread and deposition of debris during an up-cut operation.